Four hundred college students completed the Minnesota Multiphasic Personality Inventory (MMPI). A subsample with scores suggestive of psychological difficulty also were tested for platelet monoamine oxidase (MAO) and for averaged evoked response (AER) patterning. Each of these Ss also was interviewed with a structured psychiatric interview. The purpose of the study is to establish the empirical relationships among MAO, AER, and clinical symptomology. The major hypothesis is that, as with chronic schizophrenia and affective disorders, low MAO and "augmenting" AER will predict clinical symptoms of psychological difficulty in a non-hospitalized population. No research results are available at this writing.